# Underline input

> A minimal field with just a bottom line; on focus a gradient line grows out from the center.

- Category: [Inputs](https://library.aimran.es/components/inputs)
- Built with: HTML + CSS
- Live editor: https://library.aimran.es/blocks/uv-in-line
- Library: AIMRAN Library (https://library.aimran.es), free, no sign-up, by Aimran Oukham

## Where to use it

An underline input keeps the page clean, which is why designers like it for short, elegant forms: the “Your name” field of a wedding RSVP, the contact form of a photographer's portfolio or the email box in a restaurant newsletter. There is no box, just a hairline. When you click, a colored line spreads out from the middle.

Some people don't recognise a single line as a field, so keep these forms short and obvious. The placeholder disappears as soon as someone types; with more than two fields, add a visible label above each one.

## Code

### HTML

```html
<label class="uv-il"><input placeholder="Your name"><i></i></label>
```

### CSS

```css
.uv-il {
  --c1: #0071e3;
  --c2: #8ec5ff;
  --s: 16px;
  /* tamaño */
  --k: 1;
  /* velocidad */
  --fg: #1d1d1f;
  /* texto */
  --bg: #f5f5f7;
  /* fondo */
}

.uv-il {
  font-family: -apple-system,BlinkMacSystemFont,"SF Pro Text","Inter",system-ui,sans-serif;
  position: relative;
  display: block;
  width: 15em;
  font-size: var(--s);
}

.uv-il input {
  width: 100%;
  box-sizing: border-box;
  padding: .7em .2em;
  border: 0;
  border-bottom: 1px solid color-mix(in srgb,var(--fg) 20%,transparent);
  font: inherit;
  color: var(--fg);
  background: transparent;
  outline: none;
}

.uv-il input::placeholder {
  color: color-mix(in srgb,var(--fg) 40%,transparent);
}

.uv-il i {
  position: absolute;
  left: 0;
  bottom: 0;
  width: 100%;
  height: 2px;
  border-radius: 2px;
  background: linear-gradient(90deg,var(--c2),var(--c1),var(--c2));
  transform: scaleX(0);
  transition: transform calc(0.45s / var(--k)) cubic-bezier(.25,.1,.25,1);
}

.uv-il input:focus+i {
  transform: scaleX(1);
}
```

### React

```tsx
import type { CSSProperties } from "react";

const css = `
.uv-il {
  font-family: -apple-system,BlinkMacSystemFont,"SF Pro Text","Inter",system-ui,sans-serif;
  position: relative;
  display: block;
  width: 15em;
  font-size: var(--s);
}

.uv-il input {
  width: 100%;
  box-sizing: border-box;
  padding: .7em .2em;
  border: 0;
  border-bottom: 1px solid color-mix(in srgb,var(--fg) 20%,transparent);
  font: inherit;
  color: var(--fg);
  background: transparent;
  outline: none;
}

.uv-il input::placeholder {
  color: color-mix(in srgb,var(--fg) 40%,transparent);
}

.uv-il i {
  position: absolute;
  left: 0;
  bottom: 0;
  width: 100%;
  height: 2px;
  border-radius: 2px;
  background: linear-gradient(90deg,var(--c2),var(--c1),var(--c2));
  transform: scaleX(0);
  transition: transform calc(0.45s / var(--k)) cubic-bezier(.25,.1,.25,1);
}

.uv-il input:focus+i {
  transform: scaleX(1);
}
`;

export default function InLine() {
  return (
    <>
      <style>{css}</style>
      <div
        style={{
          "--c1": "#0071e3",
          "--c2": "#8ec5ff",
          "--s": "16px",
          "--k": "1",
          "--fg": "#1d1d1f",
          "--bg": "#f5f5f7",
        } as CSSProperties}
      >
        <label className="uv-il"><input placeholder="Your name" /><i></i></label>
      </div>
    </>
  );
}
```

## Prompt for AI assistants

Paste this into ChatGPT, Claude, Cursor, v0 or Lovable to adapt the block to your stack (Tailwind, Vue, Svelte…):

````text
I want to add the “Underline input” block (Inputs) from AIMRAN Library to my project.

## What it is
A minimal field with just a bottom line; on focus a gradient line grows out from the center.

## Chosen settings
- Main color: #0071e3
- Secondary color: #8ec5ff
- Size: 16px (from 12 to 24px)
- Speed: 1x (from 0.5 to 2x)
- Text: "Your name"

## What I need
1. Add it to my project with the same look and animation as the reference code: same sizes, colours, radii, shadows, timings and easing.
2. It is built with plain HTML and CSS (the reference wraps it in a React component with its CSS). If my project uses something else (Vue, Svelte, Astro, plain HTML…), translate it without losing any behaviour. If I use Tailwind, turn the styles into classes; if not, keep the CSS in its own file.
3. Expose the settings above as props (or CSS variables) with those values as defaults.
4. Make it work well on phones: nothing that depends only on hover, touch targets of at least 44 px and no overflow on 320 px screens.
5. Make it look right in light and dark mode.
6. Keep it accessible: semantic HTML, roles and aria-* where needed, visible focus and keyboard support.
7. Respect prefers-reduced-motion: with reduced motion, no big animations but the same end result.

## Reference code
```tsx
import type { CSSProperties } from "react";

const css = `
.uv-il {
  font-family: -apple-system,BlinkMacSystemFont,"SF Pro Text","Inter",system-ui,sans-serif;
  position: relative;
  display: block;
  width: 15em;
  font-size: var(--s);
}

.uv-il input {
  width: 100%;
  box-sizing: border-box;
  padding: .7em .2em;
  border: 0;
  border-bottom: 1px solid color-mix(in srgb,var(--fg) 20%,transparent);
  font: inherit;
  color: var(--fg);
  background: transparent;
  outline: none;
}

.uv-il input::placeholder {
  color: color-mix(in srgb,var(--fg) 40%,transparent);
}

.uv-il i {
  position: absolute;
  left: 0;
  bottom: 0;
  width: 100%;
  height: 2px;
  border-radius: 2px;
  background: linear-gradient(90deg,var(--c2),var(--c1),var(--c2));
  transform: scaleX(0);
  transition: transform calc(0.45s / var(--k)) cubic-bezier(.25,.1,.25,1);
}

.uv-il input:focus+i {
  transform: scaleX(1);
}
`;

export default function InLine() {
  return (
    <>
      <style>{css}</style>
      <div
        style={{
          "--c1": "#0071e3",
          "--c2": "#8ec5ff",
          "--s": "16px",
          "--k": "1",
          "--fg": "#1d1d1f",
          "--bg": "#f5f5f7",
        } as CSSProperties}
      >
        <label className="uv-il"><input placeholder="Your name" /><i></i></label>
      </div>
    </>
  );
}
```

Give me the complete final code, ready to paste, and tell me in one line where to put it in my project.
````